The present invention relates to a solar ray collecting device preferably used in space where plenty of X-rays and ultraviolet rays are present and where there is much heat radiation.
The present applicant has previously proposed various kinds of solar ray collecting devices in which solar rays are focused by a lens or the like and guided into an optical conductor cable, and further those solar rays are transmitted through the optical conductor cable onto an optional desired place for use in illumination or for other purposes.
Among the solar ray collecting devices proposed by the present applicant, there is one in which a large number of lenses, (for example, about 2000 lenses) having a diameter equal to or less than about 4 cm, are employed for focusing solar rays. The light-receiving edge of the optical fiber, having a diameter of about 0.1 mm through 0.2 mm, is precisely positioned at the focal point of each of the respective lenses so as to guide the solar rays, focused by each lens, into the optical fiber. Concerning this solar ray collecting device just described, the focal distance is equal to or less than about 4 cm. Therefore it is possible to manufacture a very thin solar ray collecting device.
On the other hand however, the focal position of the lens has to precisely coincide with the light-receiving edge surface of the optical fiber. In the case of using the device in a desert where the ambient temperature varies to a large extent in space, or in a tropical area, the lens and supporting member thermally expand so that the positional relationship between the focus of the lens and the light-receiving edge surface of the optical fiber varies greatly. In such a case it is also possible that the lens and the optical fiber or the like will be destroyed by the extreme heat generated.
In order to settle such a problem as mentioned above, the present applicant has already proposed a solar ray collecting device which is comprised of a supporting base plate on which a large number of hexagonal recesses are provided and on which a large number of optical systems are arranged on each of the recesses, each of the optical systems is comprised of a hexagonal focusing lens of a dimension that is approximately the same as that of the hexagonal recesses and the head-cut hexagonal pyramid which extends downward from the light-collecting lens as an upper surface of the recess, an optical conductor whose light-receiving surface is provided on the focus of the light-collecting lens, and the upper internal circumferential surface of the side wall, forming the recess, is so formed that it may be able to move freely on the surface of the hexagonal pyramid.
However the above-mentioned solar ray collecting device was created without taking into account the existence of X-rays, .gamma.-rays and ultraviolet rays in space, and furthermore without taking into account the special situation related to the effects of thermal energy in space, i.e. the fact that heat generated by radiation is present. For these reasons, the conventional solar ray collecting device was not satisfactory for using it in space.